The width of the deck in flat cars is dictated by AAR clearance restrictions at the center of the car. In the car bolster-truck area, the truck side rotation about the center plate limits the vertical component of the side sill below the deck. Thus, at opposite ends of the car the movement of the truck side frames requires removal of the lower side sill flange and a portion of the inclined web. In this regard note FIG. 2A of the present application.
In the area of the car bolster-truck area there are beam longitudinal loads resulting, for example, from impacts on the coupler. There are also local loads including vertical loads and fixity moments resulting from the lading and/or autoracks or other lading mounting on the car.
Since the center sill is shallow in low level flat cars being in the area of 8 to 9 inches as compared to 13 inches or higher in other designs, it is necessary to transfer some of the beam loads and local loads out to the side sill area since the shallow center sill is not able to carry all these loads.
However, as mentioned above, the side sill is foreshortened in this area due to rotation of the truck wheels with respect to the side sill.
In order that the side sill may take the bending stresses effectively, it is desired to increase the moment of inertia of the side sill.
It further is desired to displace the neutral axis of this section downwardly as far as possible.
It also is also desired to provide a smooth transition between the car bolster-truck area and the end of the car on the one hand, and the car bolster-truck area and the main body of the flat car on the other hand.
A railway flat car is provided having a center sill extending throughout the length of the car. A deck is attached to the center sill and a side sill assembly is integrally affixed at opposite sides of the car to the deck. The side sill assembly comprises an upper side sill member adjacent the deck, and a depending vertically inclined first plate integrally affixed to the upper side sill member. The first plate is affixed to crossbearers in the main body of the car and at opposite end portions of the car. The first plate is foreshortened at least in the bolster-truck area of the car. The side sill assembly further comprises on either side of the bolster-truck area and extending through the bolster-truck area of the car, a second vertical plate transversely spaced from said first plate at the lower portion of said first plate. The second plate is preferably affixed to said first plate at the upper portion and at the lower portion thereof. At least one and preferably a pair of caps are integrally affixed at the lower portion of said second plate preferably on opposite sides thereof. The caps displace the neutral axis of said side sill assembly downwardly from said upper side sill member. Preferably one of the caps extends longitudinally farther than the other cap. A lower cover plate may be applied which joins said first plate and at least one of the caps. The caps have a cross section sufficient to carry a significant portion of the longitudinal and vertical loads applied to the car in the bolster-truck area. A significant portion of the longitudinal and vertical loads are transferred from the center sill outwardly to said side sill assemblies by crossbearers in the bolster-truck area and back to the center sill by crossbearers on the other side of the bolster-truck area.